Mobile communication systems have emerged to provide a voice service while guaranteeing mobility of a user. The mobile communication system of today has been expanded to support data services in addition to the voice service. Due to the explosive increase of today's traffic, resources are running short; more and more users are demanding higher speed services; and a more advanced mobile communication system is required accordingly.
Key requirements for a next-generation mobile communication system include accommodation of explosive data traffic, significant increase of transmission rate per user, accommodation of a significantly increased number of connected devices, very low end-to-end latency, and high energy efficiency. In order to meet the requirements, various technologies such as dual connectivity, massive Multiple Input Multiple Output (MIMO), in-band full duplex, Non-Orthogonal Multiple Access (NOMA), super wideband, and device networking are being studied.
The radio link availability of the current LTE/LTE-A system entirely depends on a network coverage provision probability, which is approximately 95%.
Furthermore, radio link reliability of the LTE/LTE-A system is assumed to be capable of providing sufficient reliability through H-ARQ retransmission by applying the block error rate (BER) 10-3 in the case of unicast data through a PDSCH regardless of a control plane (a C-plane) and a user plane (U-plane).